Fans are often used as part of a cooling system to provide cooling air flow to an electronics enclosures by drawing air from outside into the enclosure. Such fans are typically mounted inside the enclosure with an inlet of the fan exposed to the space outside the enclosure through an opening in the enclosure wall. One cause of decreased performance and inefficiency in a fan-based cooling system is air that is recirculated from the fan exhaust to the fan inlet without first flowing through the electronics enclosure, thus decreasing the amount of cooling provided to the enclosure. Recirculation may be due to factors including poor sealing between the fan inlet and the enclosure wall.
Eliminating recirculation allows a fan to provide the same amount of cooling to the electronics enclosure while rotating at a lower speed, creating less acoustic noise and less vibration, and using less energy. Recirculation has been decreased in prior devices by using baffles to direct air flow and to create greater distances or more circuitous paths between the fan outlet and the fan inlet. However, those designs do not eliminate in gaps and cracks where air leaks can occur. In some instances, a fan is removably mounted such that it in the event of failure, the fan can be hot-swapped (i.e., removed and replaced) without powering down the enclosure. However, making a fan removable to accommodate hot swapping can result in even more gaps and cracks where air leaks can occur.
The need to eliminate recirculation is particularly important in cooling high density electronics enclosures which require more cooling than lower density enclosures. Often, high performance fans are used to provide increased cooling flow for high density enclosures. However, high performance fans achieve increased cooling flow in part by operating at higher speeds and/or using more efficient airfoil shaped blades, which creates higher pressure differentials between the inlet and outlet of the fan. Therefore, any air leaks become more acute and have a more significant impact on the overall cooling capacity of the fan-based cooling system.